Modern fuel delivery systems for automotive vehicles with engines having fuel injectors have utilized an electrically driven fuel pump in the vehicle main fuel tank. Typically, the electric fuel pump is mounted either directly in the vehicle tank or, as shown for example in U.S. Pat. Nos. 4,747,388; 4,807,582; 4,831,990 and 4,878,518, is mounted within a reservoir canister received in the tank. The canister reservoir supplies fuel to the pump in the event there is an interruption in the availability of fuel from the tank, such as when, under low tank fuel level conditions, cornering of the vehicle causes sloshing or movement of the fuel away from the pump inlet and to one side or the other of tank, or when essentially all of the fuel in the main tank has been consumed or used and the tank is excessively tilted by vehicle inclination on severe grades. Typically, the output of the fuel pump is greater than that required by the vehicle engine and the excess fuel is returned from the fuel injectors to the tank or to the canister reservoir.
Typically, in a no-return fuel system, there is only one fuel supply line between the fuel pump module and an engine fuel rail or manifold distributing fuel to the individual fuel injectors, and downstream of the fuel injectors there is no line returning unused fuel from the rail or manifold to the fuel tank. In such non-return fuel systems excess fuel is bypassed directly to the tank or canister reservoir, typically by a pressure regulator usually located closely downstream of the pump outlet within the tank or by a return line when the regulator is exteriorly remote from the tank.
In the aforementioned fuel systems in which the fuel pump is mounted in a fuel canister special valving has been provided between the canister, reservoir and the pump inlet to supply reserve fuel when the main tank supply is low; see for example the above cited U.S. Pat. No. 4,747,388. In this system, a valve actuated by pump suction lift of the primary fuel filter opens to provide fuel from the canister reservoir to the pump inlet when the pump inlet is starved because of low fuel or because of movement of fuel in the main tank to one side or the other during vehicle negotiation of a curve in the road. Further examples of use of a reservoir canister and special valving for supplying reserve fuel to a fuel pump are disclosed in U.S. Pat. Nos. 4,546,750 and 5,237,977. In these systems, under conditions of low fuel in the main fuel tank a valve associated with the canister responds to inertial forces created by side swerving motion of the vehicle, and/or in response to gravitational forces caused by excessive tilting of the vehicle on hills and grades, to open and allow flow of fuel from the canister to the fuel flow passage leading to the pump to thereby prevent starving of the engine due to no or low pump inflow from the main fuel tank.
Another system for preventing starving of the fuel pump and hence the engine due to low flow from the main tank is that set forth in co-pending application Ser. No. 08/496,950, filed Jun. 30, 1995 in the name of Charles H. Tuckey and assigned to Walbro Corporation. In this system an in-tank fuel pump is mounted adjacent an in-tank standpipe reservoir receiving bypass fuel from the pump, and a restricted orifice standpipe outlet and filter media of the primary fuel filter are utilized to provide an always-open reserve fuel flow path from the standpipe reservoir to the fuel pump inlet.
However, due to the greater fuel consumption demands of larger displacement vehicle engines, there still remains the need to provide an in-tank fuel reservoir system which is capable of maintaining an adequate supply of reservoir fuel by utilizing a reservoir shut-off valve so that reserve fuel is not drained from the reservoir when not needed by the pump and yet capable of providing a greater flow capacity of reserve fuel to the pump inlet when the pump inlet would otherwise be starved because of low tank fuel level allowing movement of fuel in the main tank away from the pump inlet in response to centrifugal, inertial and/or gravitational forces acting on the main body of fuel in the tank.